The disclosure herein relates generally to apparatus and methods for hermeticity testing, and further to fabrication methods for constructing such apparatus.
Electrical circuits (e.g., integrated circuits) include many types of active and passive devices (e.g., transistors, capacitors, resistors, etc.) that may be subject to damage from moisture (e.g., corrosion and functional changes to the system). For example, moisture may affect the operation and performance of circuitry, such as sensitive circuits used in implantable medical devices (e.g., sensor circuitry, pacing circuitry, timing circuitry, etc.).
Various attempts have previously been made to test the hermeticity of electrical circuit apparatus. For example, U.S. Pat. No. 4,775,831 entitled “IN-LINE DETERMINATION OF PRESENCE OF LIQUID PHASE MOISTURE IN SEALED IC PACKAGES,” issued on Oct. 4, 1988, describes measuring the conductance and capacitance of an integrated circuit at a temperature that is above temperatures which allow moisture to condense, subsequently measuring the conductance and capacitance of the integrated circuit at a temperature that allows moisture to condense, and comparing the two measured conductances and capacitances to determine the hermeticity of the integrated circuit. Further, for example, U.S. Pat. No. 5,606,264 entitled “MOISTURE SENSOR FOR ELECTRONIC MODULES,” issued on Feb. 25, 1997, describes utilizing a moisture sensing circuit formed of loosely spaced conductor lines consisting of migratory metal, which reacts to moisture.